Genotyping analyses Blood samples (3 ml) will be collected in ethylenediaminetetraacetic acid (EDTA) tubes and stored at -80°C. Genes and polymorphisms involved in the angiogenesis pathway and already suggested as predictors of bevacizumab response, will be chosen for the present analyses. Germline DNA extraction will be performed using QIAamp DNA Blood Mini Kit (Qiagen, Valencia, California, USA). Allelic discrimination of genes will be performed using an ABI PRISM 7900 SDS instrument (Applied Biosystems, Carlsbad, California, USA) and with validated TaqMan® SNP genotyping assays (Applied Biosystems). PCR reactions will be carried out according to the manufacturer's protocol. Genotyping will be not performed until an adequate number of events (>80% on study population) will be reported in terms of PFS.